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Author: Publisher: ISBN: Category : Languages : en Pages : 270
Book Description
The U.S. Environmental Protection Agency (EPA) estimated in 1996 that approximately 70% of the 8,336 Department of Defense (DoD) sites requiring cleanup had contaminated groundwater, usually from chlorinated solvents such as trichloroethylene (TCE) and tetrachloroethylene (PCE). Palladium (Pd) catalysis is a rapid destruction method that, in the presence of hydrogen gas, transforms many chlorinated ethylenes into ethane and some other halogenated volatile organic compounds (VOCs) into their respective hydrocarbon compounds. The dechlorination reactions for chlorinated ethylenes are complete and rapid and occur in water under ambient temperature, pH and pressure conditions. Hydrogen gas is used as the reducing agent, with residence times on the order of minutes. Catalytic contaminant destruction in a one-pass process has many potential advantages such as eliminating the secondary waste stream created by other processes that transfer contaminants to another medium (e.g. air or activated carbon). The technology is also effective in areas of high contaminant concentrations making it applicable to source control. The objective of this project was to demonstrate the feasibility of catalytic destruction of chlorinated VOCs in groundwater using reactors containing palladium-coated beads that were operated in-situ within two previously established horizontal flow treatment wells (HFTWs). Although installation of the reactors inside the treatment wells could be possible in a full scale application, it is not recommended due to complications associated with installing feed lines for backflushing and regenerating reactors coupled with high costs for removing reactors from the wells for maintenance, leak checks, etc.
Author: Publisher: ISBN: Category : Languages : en Pages : 270
Book Description
The U.S. Environmental Protection Agency (EPA) estimated in 1996 that approximately 70% of the 8,336 Department of Defense (DoD) sites requiring cleanup had contaminated groundwater, usually from chlorinated solvents such as trichloroethylene (TCE) and tetrachloroethylene (PCE). Palladium (Pd) catalysis is a rapid destruction method that, in the presence of hydrogen gas, transforms many chlorinated ethylenes into ethane and some other halogenated volatile organic compounds (VOCs) into their respective hydrocarbon compounds. The dechlorination reactions for chlorinated ethylenes are complete and rapid and occur in water under ambient temperature, pH and pressure conditions. Hydrogen gas is used as the reducing agent, with residence times on the order of minutes. Catalytic contaminant destruction in a one-pass process has many potential advantages such as eliminating the secondary waste stream created by other processes that transfer contaminants to another medium (e.g. air or activated carbon). The technology is also effective in areas of high contaminant concentrations making it applicable to source control. The objective of this project was to demonstrate the feasibility of catalytic destruction of chlorinated VOCs in groundwater using reactors containing palladium-coated beads that were operated in-situ within two previously established horizontal flow treatment wells (HFTWs). Although installation of the reactors inside the treatment wells could be possible in a full scale application, it is not recommended due to complications associated with installing feed lines for backflushing and regenerating reactors coupled with high costs for removing reactors from the wells for maintenance, leak checks, etc.
Author: Manuel Fernandez Publisher: ISBN: 9781423531098 Category : Groundwater Languages : en Pages : 106
Book Description
Conventional technologies for the treatment of groundwater contaminated with chlorinated solvents have limitations that have motivated development of innovative technologies. One such technology currently under development involves using palladium-on-alumina (Pd/Al) as a catalyst to promote dechlorination. Pd/Al catalyst may be used in-well as part of a re-circulating horizontal flow treatment well (HFTW) system. An HFTW system involves two or more dual-screened wells, with in-well reactors, to capture and treat contaminated groundwater without the need to pump the water to the surface. In this study, objective and fitness functions, based on system costs and TCE concentration requirements, were developed to optimize a dual-well HFTW system with in-well Pd/Al reactors in a two-aquifer remediation scenario. A genetic algorithm (GA) was coupled with a three dimensional numerical model of contaminant fate and transport to determine optimized HFTW control parameters (well location, pumping rate, and reactor size). The GA obtained a solution within the specified constraints, but the solution was an artificial solution, as contaminated groundwater in one of the two aquifers received no treatment. Based on these results, new objective and fitness functions were developed in an effort to determine the most cost effective solution to remove contaminant mass from the aquifer. The solution arrived at using this approach, while resulting in minimized values of cost per contaminant mass destroyed, produced unacceptably high downgradient contaminant concentration levels. We conclude that by specifying that only two wells could be used in the HFTW system, we overconstrained the problem and that a multi-well HFTW solution is required.
Author: Hans F. Stroo Publisher: Springer Science & Business Media ISBN: 1441914013 Category : Technology & Engineering Languages : en Pages : 807
Book Description
In the late 1970s and early 1980s, our nation began to grapple with the legacy of past disposal practices for toxic chemicals. With the passage in 1980 of the Comprehensive Envir- mental Response, Compensation, and Liability Act (CERCLA), commonly known as Sup- fund, it became the law of the land to remediate these sites. The U. S. Department of Defense (DoD), the nation’s largest industrial organization, also recognized that it too had a legacy of contaminated sites. Historic operations at Army, Navy, Air Force, and Marine Corps facilities, ranges, manufacturing sites, shipyards, and depots had resulted in widespread contamination of soil, groundwater, and sediment. While Superfund began in 1980 to focus on remediation of heavily contaminated sites largely abandoned or neglected by the private sector, the DoD had already initiated its Installation Restoration Program in the mid-1970s. In 1984, the DoD began the Defense Environmental Restoration Program (DERP) for contaminated site assessment and remediation. Two years later, the U. S. Congress codified the DERP and directed the Secretary of Defense to carry out a concurrent program of research, development, and demonstration of innovative remediation technologies. As chronicled in the 1994 National Research Council report, “Ranking Hazardous-Waste Sites for Remedial Action,” our early estimates on the cost and suitability of existing techn- ogies for cleaning up contaminated sites were wildly optimistic. Original estimates, in 1980, projected an average Superfund cleanup cost of a mere $3.
Author: Kerry J. Cadena Publisher: ISBN: 9781423514091 Category : Groundwater Languages : en Pages : 90
Book Description
Groundwater and soil contamination is a significant problem throughout the nation, with approximately 300,000 to 400,000 sites affected (National Research Council, 1994). Examples of groundwater contaminants of special interest to DoD and AF installations include fuel hydrocarbons, chlorinated hydrocarbons, and nitroaromatic compounds. Traditional remediation technologies, which include pump-and-treat, pen%permeable reactive barriers, and natural attenuation, have numerous drawbacks associated with them. These drawbacks have prompted researchers to look for innovative contamination clean- up methods. The technology investigated in this thesis, reticulating horizontal flow treatment wells (HFTWs) with in-well palladium (Pd) catalyst reactors, offers the potential for destruction of groundwater contaminants commonly found at USAF and DoD installations at less expense, more safely and effectively, and without the need to pump contaminated water to the surface, In this study, a numerical model was used to simulate application of the remediation technology under different site conditions for a number of contaminants of interest. It was found that the HFTW system with in-well Pd catalyst reactors had potential to remediate groundwater contaminants of DoD interest. Based only on this modeling study, however, it was unclear whether the technology could reduce contaminant concentrations enough to meet regulatory standards downgradient of the treatment system. Further experimental study is recommended, both in the laboratory and in the field, to quantify the efficacy of the technology in treating various contaminants of concern.
Author: Jeffrey C. Parr Publisher: ISBN: 9781423511878 Category : Groundwater Languages : en Pages : 155
Book Description
Groundwater contamination by perchlorate has recently been recognized as a significant environmental problem across the United States, and especially at Department of Defense facilities. In this study, a model is used to evaluate the potential of a innovative in situ bioremediation technology using Horizontal Flow Treatment Wells (HFTWs) to manage perchlorate-contaminated groundwater. The technology uses HFTWs to mix an electron donor into perchlorate-contaminated groundwater in order to promote reduction of the perchlorate by indigenous microorganisms in bioactive zones within the aquifer, as well as recirculate the contaminated water between treatment well pairs to achieve multiple passes of contaminated water through the bioactive zones. The model used in this study couples a three-dimensional fate and transport model, which simulates advective/ dispersive transport of solutes induced by regional groundwater flow and operation of the HFTW's, with a biodegradation model that simulates perchlorate reduction, as well as reduction of competing electron acceptors in the groundwater, by indigenous microorganisms. The model was applied to an example site to demonstrate how in situ perchlorate treatment might be implemented. A sensitivity analysis using the model is also conducted to evaluate which engineered and environmental parameters most affect technology performance. Model simulation results demonstrate that this technology may be effective in managing perchlorate-contaminated groundwater. The recirculation induced by the HFTW system results in increased treatment efficiency, as compared to treatment that would be achieved by a single pass of contaminated water through the bioactive zones. It was observed that the model was very sensitive to several kinetic parameters, indicating that a fruitful area for future research would be to study how these important parameters can be accurately quantified for given geochemical and microbiological conditions.
Author: Peter G. Chosa Publisher: ISBN: 9781423518594 Category : Bioremediation Languages : en Pages : 193
Book Description
Perchlorate contaminated groundwater is rapidly becoming a significant environmental remediation issue for the Department of Defense. In this study, an existing numerical model that simulates the operation of a Horizontal Flow Treatment Well (HFTW) system to effect the in situ biodegradation of perchlorate through the addition of an electron donor is modified to include a submodel that describes bioclogging. Bioclogging restricts flow out of the HFTW due to the accumulation of biomass directly adjacent to the well. The modified model is then applied to an existing perchlorate contaminated site that will be used for an evaluation of the HFTW technology. Simulations were conducted to determine the impact of altering various engineered parameters on HFTW performance. Simulation results indicate that higher time averaged electron donor concentrations and HFTW pumping rates lead to more perchlorate degradation in terms of total mass of perchlorate removed. Simulation results also indicate that varying the electron donor addition schedule has little impact on HFTW performance. The simulations conducted in this study show that, regardless of the engineered parameter values, bioclogging does not impact the ability of the HFTW technology to effect in situ biodegradation of perchlorate at the evaluation site.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A system for remediating groundwater contaminated with halogenated solvents, certain metals and other inorganic species based on catalytic reduction reactions within reactive well bores. The groundwater treatment uses dissolved hydrogen as a reducing agent in the presence of a metal catalyst, such a palladium, to reduce halogenated solvents (as well as other substituted organic compounds) to harmless species (e.g., ethane or methane) and immobilize certain metals to low valence states. The reactive wells function by removing water from a contaminated water-bearing zone, treating contaminants with a well bore using catalytic reduction, and then reinjecting the treated effluent into an adjacent water-bearing zone. This system offers the advantages of a compact design with a minimal surface footprint (surface facilities) and the destruction of a broad suite of contaminants without generating secondary waste streams.
Author: Bernard H. Kueper Publisher: Springer Science & Business ISBN: 1461469228 Category : Technology & Engineering Languages : en Pages : 759
Book Description
The purpose of this book is to help engineers and scientists better understand dense nonaqueous phase liquid (DNAPL) contamination of groundwater and the methods and technology used for characterization and remediation. Remediation of DNAPL source zones is very difficult and controversial and must be based on state-of-the-art knowledge of the behavior (transport and fate) of nonaqueous phase liquids in the subsurface and site specific geology, chemistry and hydrology. This volume is focused on the characterization and remediation of nonaqueous phase chlorinated solvents and it is hoped that mid-level engineers and scientists will find this book helpful in understanding the current state-of-practice of DNAPL source zone management and remediation.
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Author: Manuel Fernandez
Author: Hans F. Stroo
Author: Kerry J. Cadena
Author: Jeffrey C. Parr
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Author: Peter G. Chosa
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Author: Bernard H. Kueper